Rotative winged aircraft



July 20, 1943. 1 A. g. LARSEN ,5

v ROTAifIVE- WINGED AIRCRAFT Filed 0012.31, 1940 5 Sheets-Sheet 1ATTORNEY;

July 20, 1 943. Lgk I 2,324,588

ROTATIVE WINGED QXIRCRAFT Filed Oct. 31, 1940 5 Sheets-Sheet 2 L I 'I l5l5 INVENTOR ATTORNEYS A. a. LARSEN v 2,324,588

ROTATIVE WINGED AIRCRAFT Filed Oct. 51, 1940 5 Sheets-Sheet 3 4MYTEKIVH/ATE' v INVENTOR i ATTo Rlzl i iYs July 20, 1943. M

E. LAREN v 2,324,588

ROTATIVE WINGED AIRCRAFT Filed Oct. 51, 1940 s Sheets- Sheet 4 Ma F 'INVENTOR BY AQMM ATTORNEY5 July 20, 1943. A. E. LARSEN 2,324,533

V ROTATIYVE WINGED AIRCRAFT Filed Oct. :51, 1940 5 Shet's-Sheet s I wdz; 11. 5 a I15 I15 1 INVENTOR ATTORNEYS Patented July '20, 1943-2,324,588 "aorarrvr: wmosn Antcnm E. Larsen, Jenkintown, Pa., assignorto Autogiro Company of America, Willow Grove, Pa a corporation ofDelaware Aplluclfloll October 31, 1940 Serial N0. 363,593

fli ht and take-oi! and also increasing the safety 31Claims.

This invention relates to rotative wingedaircraft, and is particularlyconcerned with a control' system for that type of rotative wingedaircraft which isicapable of effecting what has become known in the artas direct take-oil, i. e., take-oi! generally vertically from the groundor at a steep angle. The invention, moreover, is

especially adaptable to that type of rotary wing aircraft in which aforward propulsion airscrew is employedfor translational flight and inwhich, during such translational flight, the rotor is adapted to beautorotationally or aerodynamically rotated} p t In aircraft oftheclassabove referred to, di-

rect take-01f is ordinarily effected by mechanically driving the rotorwith the craft at rest on the ground and with the blades of therotorreduced to a non-lifting pitch angle, preferab y zero pitch, in order tominimize rotational drag. Upon the attaimnerit ofa relatively high R. P.M.,

- preferably considerablyin excess of the normal R. P. M. ofautorotational flight. the rotor drive is disconnected and therotorblade pitch angle is increased, in consequence of which'the excesskinetic energy stored in the rotor is converted to lift and the machineis caused to rise vertically rromthe ground or at least at a very steepangle.

While a take-off similar to the above may be effected in an aircraft inwhich the rotor drive is not normally disconnected in flight, in thatevent some means (such as two rotors driven in opposite directions)isnecessary in order to counteract the rotor driving torque. Certainfeatures of the present invention are applicable to aircraft of thislatter type, although'it is also to be noted that other features areparticularly suited to the factor by making; it impossible for the pilottoincorrectly adjust certain of the controllable devices. l a

In considering the foregoing objects of the invention, itshould be keptin mind that th e points mentioned are of especial importancebe cause ofthe fact that the direct take-oft maneuver consumes only a matter of afew seconds time, during which the pilot obviously would. not

have opportunity to correct for maladjustment of one or moreindividually operable controls.

with the foregoing more for less general objects in view, the inventionprovides a single control for conjoint operation of .themechanism foradjusting blade pitch angle and of the device for connecting anddisconnecting the rotor'drive, the operation of these two units beingcorrelated in that sense providing for blade pitch reduction when therotor drive is connected and for blade pitch increase when the rotordrive is disconnected. In accordance with another aspect,

the invention contemplates interlocking the operation of the commoncontrol above referred to with the control for. the rotor brake and alsopreferably with the control for the wheel brakes, the sense of thisinterlock being such that the rotor drive clutch cannot be engaged at atime when the rotor brake is applied, and further such that the rotordrive clutch cannot be engaged unless the wheel brakes are applied.

Another object of the invention is the provision of a safety deviceautomatically operative upon the aircraft leaving the ground to rendertype in which the rotor drive-is disconnected at or just befor take-oil.a

Certain aspects of the invention are still further concerned withaircraft of the types mentioned. above having a rotor brake and alsowheel brakes.

Generally stated, the principal object of the present invention is theprovision of an effective and fool-proof control system for various ofthe devices of the craft mentioned hereinbefore, the said system beingcapable of operation by the pilot in a very simple manner, therebyensuring proper conditions for efiectin'gthe maneuvers intended by thepilot.

More specifically, the invention has in view a simplified control systemautomatically interrelating the'operation of various devices of thecraft, thereby simplifying the manipulations of 5 the control systemineffective to engage the rotor driving clutch in flight or to reducethe rotor blade pitch angle. A portion ofthis same. safety mechanism isalso employed in accordance with the invention as a means to effectreduction .of rotor blade pitch angle automatically upon landing of theaircraft, thereby avoiding unintentional re-take-oil or the like underthe influence of a wind gust.

The control system of this invention still 7 further incorporates servodevices for utilizing fluid pressure developed by a'l ump driven by theengine in order to applythe rotor brake or the wheel brakes, orboth, therotor and wheel brakes also being equipped with additional meansproviding for manual application of these brakes in the event of enginefailure.

With a view to still further simplifying the necessary manipulations ineffecting take-off, the invention contemplates use of a control for therotor blade pitch angle and the rotor driving clutch associated with thethrottle for the engine and arranged so that the pilot may trip thecontrol (thereby increasing blade pitch and disconnecting the rotordrive clutch) with the same hand with which he operates the enginethrottle. This is of importance since, in the direct takeoff maneuver,it is ordinarily desirable for the pilot to' adjust the. engine throttleto. increase the engine speed at or just before the moment of take-off.With a control located on the engine throttle there need be no loss oftime (and, therefore, of the kinetic energy stored in the rotor) betweendisconnecting the rotor drive and adjusting the throttle to'i'nc'reasethe engine speed.

Since it is desirable, at least under certain conditions, to effecttake-off after a short run on the ground, the invention provides acontrol system in which the operations of disconnecting the rotor driveclutch and increasing the blade pitch angle are effected sequentially.vTheinvention also has in view manual operation of the control system ina manner introducing a time interval between rotor clutch disconnectionand blade pitch increase. Still further, the invention contemplates theprovision of automatic time delay mechanism for this purpose.

How the foregoing and other objects and advantages are secured will bemore apparent from the following description referring to theaccompanying drawings, in which .Figure 1 is a schematic diagram of thecontrol system of the present invention including a showing of theprincipal devices and units of the aircraft with which the system isassociated;

Figure 2 is a plan view of some of the control organs, certain partsbeing shown in horizontal section for clarity;

Figure 3 is a vertical section taken as indicated by the section line3-3 on Figure 2;

Figure 4 is a vertical sectional view through the main or master controlvalve associated with that portion of the control system connected withthe rotor blade pitch changing devices and with the rotor drive clutch,this view being taken as indicated by the section line 44 on Figure 5; a

Figure 5 is a cross sectional view of the master control valve taken asindicated by the line 5--5 on Figure 4;

Figure 6 is a view, partly in elevation and partly in vertical section,of one of the control units, including the servo control, employed foroperation of the rotor brake and the wheel brakes;

Figure 7 is a transverse sectional view through portions of the rotorand airscrew transmission, illustrating a fluid pressure control deviceassociated with the transmission;

Figure 8 is a longitudinal sectional view through the control deviceillustrated in Figure '7;

Figure 9 is a fragmentary view similar to Figure 1 but illustrating amodification;

Figure 10 is a somewhat diagrammatic layout of another form of controlsystem incorporating a modified master control valve; and

Figure 11 is a wiring diagram of a control system similar to Figure 10but incorporating additional features hereinafter fully described.

In the diagram of Figure 1 the various principal devices and elements ofthe aircraft are indicated in their approximate relative positions. Thusa blade of the sustaining rotor appears at R toward the top of thefigure, a pair of landing wheels W-W appearing toward the bottom. To--viewed in Figure 1) thereis a pair of tandem coaxial airscrews A-A. Theairscrews and rotor are all adapted to be driven from the engine Ethrough a transmission '1'.

Various features of the major units referred to just above need not beconsidered in detail herein. since they form no part,of thepresentinvention per se. It is to be inderst'ood, however, that the blades ofthe rotor are connected with the rotor hub by means of mounting pivotsand devices providing freedom for pitch change movement of the blades,and preferably also for flapping and"drag movements of the blades.Mechanism suitable-for the purpose just mentioned is disclosed in mycopending application Serial No. 271,841, filed May 5, 1939, now PatentNo. 2,264,942, issued December 2, 1941, and

also in Patent No. 2,216,163, issued October 1,

A brief description of a suitable blade mounting (as disclosed, forexample, in the aforesaid copending application andissued patent) ishere given to aid in, an understandinglof the operations effected by thecontrol system of the present invention. Each blade is connected withthe hub by means of a pair of external and internal cooperatingthreaded. parts the axis of which is coincident with the longitudinalaxis of the blade. The sense of the threading and the thread angle aresuch that the action of centrifugal force on the blade tending to drawthe blade radially outwardly causes the blade to turn on the threadedmounting in a direction to increase its pitch angle. Movement oftheblade on this mounting to reduce the pitch angle is effected by thecontrol system hereinafter described,

In connection with the transmission T, it is to be observed that anappropriate form of transmission is fully disciosedin copendingapplication of Robert G. Anderson, Serial No. 235,448,..nled October 17,1938, now Patent No. 2,217,883,-issued October 15, 1940. Many featuresof this transmission need not be considered in detail herein since theyform nopartof the present invention per se, but it should .be kept inmind that the transmission receives power from the engine E and servesto drive the airscrews A in opposite directions. For starting the rotor,the transmission incorporates a disconnectible clutch by means of whichthe rotor drive shaft may be coupled with the engine so as to deliverpower to the rotor. A few other features'of the transmission will bereferred to more fullyhereinafter.

With the foregoing general arrangement of parts in mind, attention isnow directed to the control system as ,illustrated in the diagram ofFigure 1. The system in general is of the hydraulic type, the pressurebeing developed by a pump 9 connected with some part of the transmissionwhich always-rotates with the engine E. A reserve'tank l0 serves to keepthe system supplied with pressure fluid, ordinarily oii, the inletconnection to the pump being indicated at H. The outlet connection 12from the pump-extends to one port of the master control valve IS. Areturn line ll connects another port of the valve IS with the inlet lineH for the pump. f

Valve I3 has two additional ports one communicating with a connection I5which is extended to a fluid pressure piston and cylinder device 16connected with an arm l1. through which the device- I5 is effectivetoalter the'blade pitch from a higher. to a lower pitch setting.

ward the front of the machine (to the left as The last of the ports ofvalve I3 is coupled by means of connection II andbranch I30. withtwo'portions of a piston and cylinder devicegenerally indicatedat l3.i'orcont'rol'ot sion parts {as will be described hereinafter withparticular reference to'Figure 7.

A by-pass is provided betweenthe outlet pressure) side of the pump 3 andthe inletside there-g of. This lay-pass includes a pipe coupled with thepressure line l2, valve II and connections 22andt23. the latterdelivering to the reserve certain transmisi when, viewed as 'mission.

blades and to the costar device is or the em,

soas to enable starting or the rotor in preparation for member 40 isrotated in a clockwise direction; in Figures i and 4, the initialmovement connects pipe I. with pipe l4 (through the valve channel 4:thereby dissipating the pressure previously applied to the transmissiontank It. The valve 2| inthisby-passconnection tion provides shut-ofl ofthe by-pass when" the aircraft is at rest on the ground and opening ofthe by-pass when the craftis in the air, the

control device l3. Further movement of the valve 4 member 40 in theclockwise direction connects pipe II with pipe l4 (through channel 43)with the result that the pressure in the rotor pitch reasons andoperations involved being described more fully hereinafter. t M i I Eachof the landing wheels illustrated is provided with a wheel brake 28adapted to be actuated by a piston and cylinder device 29 supplied withpressure through branches 30a of connection 30, the latter beingassociated with the wheel brake control unit indicated generally at 3|.i i

Similarly, the sustaini'ma rotor is provided with a rotor brake32.actuable by a device 33 receiving fluid pressure through connection.34 which is associated with the rotor brake control unit generallyindicated at 35. Fluid is supplied to the rotor and wheel brakeactuating systems from a' source of fluid independent of that firstmentioned; Thus, as shown in Figure 1, the rotor and wheel brakesourceofgfluid includes a reserve tank 36 and connections 31 and 38 extended respectively to the wheel brake unit 3| andthe rotor brake unit.35.

Each of units 3i and incorporates aservo control adapted to beactuatedbyfluidfunder pressure'supplied from the pump 9. .To this end a pipe l2ais connected withxthe pressure line l2 driven shaft and the rotor driveshait'india 235,448, the transmission controlling devices is dissipated.

Atlthis point attentionisdirected to thedis closure of Figures 7 and 8illustrating the co!!- trol unit l3 and its connections'with devices in"the transmission T. As above mentioned (and as disclosed in thecopending application 235,448 referred to), the transmissionincorporates a the rotor drive, this disconnectible' clutch: in clutchbeing interposed between the engine cated at 45 (see Figure 1) and beingcontrollable by an arm 4! mounted on shaft 48. Still further, asdisclosed.in copending application incorporates a planetary gear system"interposed in the drive between the engine driven shaft 45 and theairscrews A-A. The planetary system, moreover,

is adapted to provide two speeds of airscrew drive for a given enginespeed. When the rotor lsbeing driven the planetary systemis'notoperative and the transmission gearing then providesrelatively lowairscrew R. P. Mufor a given engine R. P. M.; and whentherotor clutch isdisengaged the planetary system provides a higher gear ratio inthetransmission to the airscrews. v

The details of this gearing need not be considered herein,but it isimportant to note that through a reducing valve l2b, pipe Ila beingprovided with a pair of branches He and 12d 1 communicating respectivelywithnthe 1 control units 3| and 35. The return side of this servo,

system includes a pipe 23a connected with bypass line 23 and havingapair of branches 23b and 23c extended respectively to the units 3| and35. n t n The rotor and wheel brake control units 3| and 35 areessentially similar in construction,

one of them being described in detail hereinafter with reference toFigure 6. y

In taking up thedescription of various of the control units attention isfirst directed to the showing, in Figures 2, 4 and 5,; of the mastercontrol valve l3. 'I'hisvalve comprises a casing 39 having a chambertherein adapted to receive in the change-over from the first conditionto the second condition just mentioned one of the gear members of thetransmission is subjected to abraking' force to arrest its rotation,this member being indicated in Figure 'l at 49. Figure 7alsoillustratesa brake band surrounding member 49'and adapted beoperated by an arrn5l pivoted at 52, the two endsof the brake band beingcoupled with this arm by pins The showing of Figures 7 and 8 alsoincludes the clutch controlling arm 4'! and shaft 43.

The control unit "19 which appears in section in Figure 8 incorporatestwo independently'rnovable piston devices and 56, the first of which isarranged in cylinder 51 and the second incylinder 58. Piston 55 isprovided with a stem 53 projecting at the lowerend of unit l9 andcoupled with the arm 5| for operating brake 50 by means eaten at as and44, these channels being ranged to provide for the operation describedjustbelow. n i V In theposition of the valve indicated in Figures 1 to 5inclusive, the pressure line I! from the pump 9 is connectedwith pipesi5 and it (through channel 44) which extend, respectively, to the pitchcontrol devices i6 for the rotor nection I3 (seealso Figural).

of a pin 60. Piston 561s slidable onstem 59 of the-first piston and isconnected with a yoke 6| whichcprojects from the lower end of unit l9.Yoke 6], in turn, is coupledwith the clutch actuating arm 41 as by a pin62. A cup 63 at the lower end of unit 19 is provided with aperturesadapted to guide the stem and the Fluid pressure is delivered tocylinder 51 through connection I 8a and to cylinder 58 through con- Fromthe above it will be seen that sion, 1. e., connection and disconnectionoi. the rotor driving clutch and application and release g i Thisprovides for decrease oi rotor blade pitch and for connection of therotor drive clutch,

direct take-oil. Asthe valve this control unit lsperforms-two functionsin the transmisof the brake band 58, whichlatter serves a the uneans forchanging the gear ratio in the transmission to the propulsive airscrewsA--A.

It should now be noted that the control hookup is such that the rotordrive clutch is engaged and the brake band 50 is conjointly releasedupon admission of pressure to connection [8, as when the master valve l3ispositioned as in all the figures (inwhich position the rotor bladepitch is also reduced). Upon rotation of valve l3 in the clockwisedirection, the pressure in connection I8 is dissipated and the rotordrive clutch is thereupon disconnected and the brake band 50 istightened. Disconnection of the clutch ,is. desirably effected by arelease spring not herein illustrated, and tightening of the brake band58 is accomplished by spring 64 which is located within unit [9 andarranged to move piston 55 upwardly. Because of the parts as justdescribed,-the conditions for normal flight (high airscrew speed, androtor .drive clutch disconnected) are maintained even in the event offailure of the fluid pressure system.

Turning now to the by-pass between the high;

and low pressure sides of the clutch and pitch control system, and withespecial reference to the by-pass valve 2|, it is to be observed thatthe master valve I3 is only effectve to deliver presarrangement of thesesure to the pitch control devices I6 and to the transmission controldevice l8 when the by-pass valve 2| is closed. This valve is, therefore,coupled with a landing wheel in such manner asto close the valve whenthe aircraft is at rest on the ground. In consequence, automaticallyupon take-ofi the by-pass valve is opened and the high pressure line I2is short circuited through pipes 20, 22 and 23, the last, of which iscoupled with the reserve tank l8.

The by-pass valve 2| serves a further important function, as follows:Since the master valve I3 is ineffective when the machine is in the air,when the pilot is approaching a landing he may adjust the valve l3 to aposition intermediate its two extremes in which the high pressure lineH. is coupled by pipe l5 with the blade pitch control devices l6. Whilein the air this will not cause blade pitch reduction, but willautomatically do so upon landing, at which time the by-pass valve 2l isclosed. thereby establishing pressure in the system and effecting bladepitch reduction. This feature is of advantage in making landings, sincethe lift of the rotor is automatically spilled" immediately uponlanding.

Reference is now made to the structure of the control units for therotor brake and the wheel brakes. Figure 6 illustrates the control unitfor the rotor brake. The portion of this unit toward the left of Figure6 comprises a cylinder 65 having a piston 66 working therein, theconnections 34 and 38 hereinbefore mentioned being associated withcylinder 65 in a well known manner in order to provide for delivery ofpressure to the brake actuating cylinder 33 upon movement of piston 66into the cylinder. The position of the parts shown in Figure 6 is thatwhich they occupy when the brake is released. Adjoining cylinder 65 isanother cylinder 61 having a piston 68 working therein, the piston stem69 being extended for engagement with piston 66. A stem' 18 projectsfrom the opposite side of piston 68, being provided with an operatingknob II. By pushing on manually moved to apply the rotor brake. Thismanual control is desirably employed only in the a'szits 'event offailure of the to be described.

A'valve casing 12 is arranged at onesidejof cylinder 61, the-casingserving to house a valve member 13 having a projectingstem Hand anoperating handle 15. Two ports I6 and 11 in the valve casing I2,communicate, respectively, with pressure and relief pipes Md and 230above mentioned. These two parts join at'a point beyond the valve 13 andcommunicate with the righthand end of cylinder 61 as .is clearly shownin Figure 6. H l 7' The valve member itself is provided with a port 18which, in the positionof the valve illustrated, is in registry with port.l'l i'an d, therefore, places the interior of cylinder 6 l,incommunication with the relief, pipeZSc. Upon manual inwarddisplacementof .the valve 1;! port 18 is servo pressure s s fim now .brought intoregistry with port 16 which places the pressure line lZdlintocommunication with the cylinder 61, therebyeffecting moveme. t of piston68 to the left. This-in turn, moves piston 66 to the left which appliestherrotorbrake.

= Valve 13 is biased to release position (the position shown in Figure6) bya spring 19.

Any desired adjustment of the rotor brake may lie-retained by meansofhandle, 88 journaled on the manually operable stem 10, the handle beingconnected with an eccentric bushing 8| adapted to clamp the stem 18through the split collar 82.

The structure of control unit 31 for the wheel brakes is exactly thesameas that describcdjust above in connection with Figure 6.

From the foregoing it will be seen that each of, the brake systemsiitherotor brake or the wheel brakes) .is readily operable by the servo ofthe control ll.

control handle 15, and mayv also be operated in the event of enginefailure by manual actuation Referring again to the ,control system asshown in Figure 1, itshould-now be noted that the-by-pass valve 2| notonly serves =.to render the master valve l3 ineffective when theaircraft is in flight, but further serves to render the servo controls,for the rotor and wheel brakes ineffective when the aircraft is inflight. This is a safety feature tending ,to avoid unintentionalapplication of the rotor brake or of the wheel brakes, which lattershould'ordina'rily remain released until after the wheels have touchedthe ground.

The invention providesadditional interlocks and safety featuresinterrelating the operation 1 of the rotor and wheel brake control unitswith operation of the master control valve l3. These interlocks areshown in Figures 2 and 3. As there seen, the manual controlstem '18 forthe rotor brake appears at theleft and the manual control stem 10a forthe wheel .brakes at the'right, one being located at each side of thevalve l3 in parallelism with the operating stem 4| of the valve. Thisstem-4| carries a multiplejcam 83,

one surface 84 ofwhich cooperates with a transversely slidable interlockpin 85 and the other surface 86 of whichzcooperates with a transverselyslidable interlock pin .81. The two pins 85 and 81 are mounted inanyconvenient supports such as those indicated'at 88, and each is providedwith a collar 89 and an associated springv 88 urging the pin inwardlytoward the camsur faces 84 and 86.

The stem 18 of "the rotor-brake contr'olis V equipped with aninterlockcollar 9|, and a simiknob H piston 66 may be directly lar collar 92 ismounted on thestem 1821 for the wheel brake control. The position of,these collars 9| and 82 lengthwise of the stems l0 and 10a to the bladepitch control devices. and to the control unit 'lll for thetransmission. With this adjustment, the rotor is adapted. to be driven;

and since it is undesirable at that time to permit actuation of therotor brake the c'ollarj 9| on the rotor brake control stem is locatedso that if an attempt be madetoapply the rotorbrake the interlock collarwill abut the plunger 85 1 At the other side of Figure 2 .itwill benoted that the wheel brake control stern 10d occupiestits innerposition, in which the collar 92 lies inside i the plane of plunger 81.This'is the position of wheel brake application, and at this timeplunger 81 will retain the wheel brakesapplied. H

The interlocks just mentioned further prevent movement of the valvecontrol handle 42 from the release position into the position shown inFigure 2 in either of two events. First, the control handle cannot bemoved into the position shown in Figure 2 if the rotor brake is applied,since in that eventthe collar 91 liesin the plane of plunger 85 and,therefore,xprevents outward movement of theplunger which, in turn(through the action of cam surface) prevents rotation of the controlhandle 42. Second, the control handle cannot be moved to clutch-engagedposition unless the wheel brakes are app ied, for the reason that theaxial dimension of the collar, 92 is such that plunger 81 can only bemoved outwardly by cam surface 86 when the stem 10a and its associatedcollar 92 are moved inwardly to clear plunger Because of the foregoinginterlocks, the pilot is prevented from attempting to start the rotorat" any time when the rotor brake, is applied and, in addition, he.cannot start the rotor unless the wheel brakes are applied.

At the moment of take-off, the movement of the ,control valve handlereleases plunger 81 which thereby automatically permits release of thewheel brakes. r at Since it is desirable to permit thepilot to set 5 ofFigure 1) the master control. valve 13 is equipped with an arm 93, thevalve here being biased by a spring 94 to provide for automatic movementthereoffrorn the rotor drivingposi tion tothe flight position, A latch951s adapted to cooperate, with arm93 and is controllable by a solenoid95 the operating circuit 91 of; which may be completed by a.thumb'button 98 mounted at the top of the hand grip 99 of athrottlecontrol lever 100 for thefengineE.

, In effecting direct take-off, it is ordinarily desirable toopen thethrottle to increase the en"- Eine speed at or just before the moment oftakeofi. With the arrangement of. Fiure 9, when preparing to effect thetake-oil, the pilot may place one hand on the throttle ommune otherbeingused at the flight control wheel. or stick) and when the rotor hasbeen accelerated, to the desired speed, the button 98 may be actuated torelease the control valve I3, and without moving his hand from onecontrol to another, the pilot may immediately advance the throttle toincrease the engine speed. v 1

In. considering the operation of the control sys tem already described,it is to be noted that the master control valve is arranged to providesthe master control valve to its intermediate posi tion in preparationfor making a landing (in which position pipe. I 2 is connected with theblade pitch reducing devices l6), and: since thewheel brakes should notb applied when making a landing, the cam surface 88 for actuationiof thewheel brake interlock pin 81 is so shaped that the pin 81 is not movedoutwardly to its interlocking position until after themaster valve haspassed. the pitch-decrease p sition. Thus. as

shownin Figure 5, the cam surface 06 is divided Another feature servingtosimplify. the con trol operations is illustrated in Figure 9. In thisview (showing a portion ofthe control ystem position and the position ofpitch- ,below.

quential rotor clutch disconnection and blade pitchincrease when atake-oil? isbeing made. I

While in the manually operable arrangement of Figure, the master controlvalve may be moved toefiect take off atany desired rate, in the,arrangement of Figure 9 the rate ofmovement would, of course, bepredetermined by the charactciristics of the returnspring and of thevalve itse f.

In any event, the sequence referred to (clutch disconnection precedingblade pitch increase) is ordinarily desirable in efiectingftake-oifsince clutch disconnection is also accompanied by increase of airscrewspeedwhich will, therefore,

Where the master valve isentirely manually operable, as in Figure 1,thislead in disconnection of the clutch (and build-up, ofairscrewthrust) may .be extended by the pilot, merely by initially moving thecontrol valve to its intermediate position and thenpausing for anappropriate interval before continuing the movement of the valve toincrease the blade pitch. With the wheelbrake interlock as describedwithreference to Figures 2 and 3, the mam movement of theImastervalv'ewill also permit automatic release of the wheel brakes, in view of whichaverysteep and high take-off jump may b eifectedfollowing a short runonthe ground. I i i This timed or delayed take-olfis desirable, atleast'under certain conditions, and with thisin mindjthe invention further' contemplates mployrnent oi the alternative modified forms ofcontrol system, such as that described hereinafter with reference toFigures 10 and 11. i Referring first to Figure 10, it is to be observedthat the master control valve indicated generf ally at llll is of theaxially movable piston type comprising a valve casing I02 inwhich thevalve member IN is arranged for "movement to establish and cut offcommunication between various chambers in the valve casing as describedhere- With reference to the valve chambers just mentioned, it maybenoted that the piping sys tem contemplatedin accordance with thearrangement of Figure 10 is generally the same as that illustrated inFigure 1. The pressure line the valve member I03 is manuallycontrollable through its stem I08 having a control knob IIO.' When thevalve is positioned as in Figure 10, the pressure line I2 is connectedwith the return line I4 through chambers I04 and I01. As the knob H isdrawn outwardly to the position in which valve member I03 lies betweenchambers I and I06, an additional valve part I I I moves forwardly toblock communication between chambers I04 and I01, thus shutting ofi thecommunicatiomoi the pressure line with the release line. In this secondposition, moreover, communication is established between chambers I04and I05 with the result that pressure is delivered to the blade pitchcontrol line I5, thereby effecting blade pitch reduction. As the valveis advanced still further,

so that member I03 lies between chambers I06- and I08, pressure isadmitted to chamber I06 and from there to the clutch control line I8. Inthis last position it should be noted that the valve member I03 blockscommunication between chambers I06 and I08, thereby preventing releaseof pressure through the branch release line I4b.

From the above it will be seen that this master valve IOI provides forcontrol in the same general manner as that described hereinbefore. Inthis arrangement, however, the master valve is preferably biased torelease position, i. e., the position shown in Figure 10, by means of areturn spring II2 disposed in a casing 211 at one end of the valve. Atthe opposite end, .the valve member is provided with an extension II3,the end portion of which is cut away at one side to form a shoulder II4.At its other side the ex.- tension H3 is notched as at II5. Shoulder H4and notch II5 are adapted to cooperate, respectively, with solenoidlatch controls H6 and H1.

The armature IIB of solenoid II6 has its end formed as a latch adaptedto cooperate .with shoulder H4, part II8 being urged toward its positionof engagement by means of a spring 9. Similarly, the armature I ofsolenoid H1 is formed as a latch to cooperate with notch II5, thisarmature being urged toward its position of engagement by means of aspring I2I.

The control circuit for solenoid II6 comprises connections I22 and I23,the latter of which is associated with a source of current B. ConnectionI22 is extended to a control switch I24, this circuit being completedthrough connection I25 extended to the source of current.

Similarly, solenoid II1 has a circuit including wires I26 and I21, thelatter extending to the source of current B, and the former to a controlswitch I28. Connection I29 completes this circuit.

The control switches I24 and I28 are desirably mounted close to, andpreferably on, the pilots flight control, such as the steering wheelI30, thereby facilitating operation of the switches. It is to beunderstood that this wheel I30 serves for longitudinal and lateralcontrol of the aircraft in flight, the same being coupled with rotorcontrols in the manner fully set out in my copending application SerialNo. 209,511, filed May 23, 1938, now Patent No. 2,273,051, issuedFebruary 17, 1942.

In describing the operation of the system of Figure 10, it is firstpointed out that shoulder H4 is positioned axially of the valve so thatengagement with the armature II 0 of solenoid 5 II 6 takes place whenthe valve member I03 is positioned between chambers I05 and I00.Additionally, it is to be noted that notch H0 is so positioned as toengage armature I20 0! solenoid II1 when valve member I03 lies betweenchambers I06 and I00.

In operation, therefore, when it is desired to initiate rotation of therotor on the ground prior to effecting direct take-oil, the control knobH0 or the master valve MI is drawn outwardly until notch I I0 is engagedby armature I20. This provides for blade pitch reduction and actuatesthe control unit I0 (see Figure 1) oi the transmission so as to providelow speed airscrew drive and so as to connect the rotor drive clutch.When 20 the desired rotor R. P. M. has been attained, the

switch I20 is actuated to release armature I20 from notch H6 and thereturn spring II2 oi the master valve then causes the valve to moveinwardly to the position in'which the rotor drive 25 clutch isdisconnected and in which the airscrew speed is increased. At theappropriate moment, usuallya couple of seconds after release of therotor clutch, the other control switch I24 is then actuated in order towithdraw the armature H0 30 from shoulder II4, this operation permittingthe return spring I I2 to move the valve all the way to its releaseposition, in which the blade pitch is increased and the take-of!eflected.

The system of Figure-10, therefore, places the 5 timing of the take-oi!and the take-oi! run, it

any, in the handsoi' thepilot.

If desired, the pilot may operate this system in a manner essentiallysimilar to that provided by the system oi. Figure 9. This may be doneeither by simultaneously actuating both of the control switches I24 andI20 at the moment desired for take-oil, or by preliminarily holding down(on) switch I24 and then, subsequently, actuating switch I28 at themoment desired for take-oft. v V

In accordance with a further feature of Figure 10, the rotor brake andwheel brake interlocks are also associated with the master valve IOI.For this purpose the interlock plungers 05 and 01 are associated with acam III, of which cam curface I32 corresponds to and functions'in thesame manner as cam surface 04 of Figure 3. (At the other side, camsurface I33 corresponds to and functions in the same manner as camsurface 86 shown in Figure 3. It is here noted that cam surface I33, asin the arrangement first described, is shaped so as to delay actuationof the wheel brake interlock plunger 01 until the knob IIO of themastercontrol valve is drawn outwardly beyond the position providing forblade pitch reduction.

The system 0! Figure 11 is similar to that of Figure 10, employingthesame type of master control valve IN, and with solenoids I I6 and II1 for actuating latches for control of valve movement from the on" tothe of! position. In Figure 11, however, only a single control or tripswitch is used. Although this switch is here shown as mounted inassociation with the control wheel I30, it is to be understood that itmay take the form of and be mounted in accordance with the showing ofFigure 9, wherein acontrol or trip switch is mounted on the throttlelever vfor the engine.

The control switch is here identified by the numoral I 34, theswitchbeing associated with a circuit includingwires I 26, and I21 extended tosolenoid II1, as in Figure 1 0. The solenoid H6 however, is actuatedthrough a time delay relay gencrall'y'indicatcdat I35. One terminal ofthis relay is coupled byconnection I36 with wire I26, the other terminalbeing coupled by connection I31 with thecontrol member I38 of acominstance applicant contemplates use of these conbined switch andrheostat. The resistance I39 of this rheostat is"connected.with wire I21by means of connection I40, the arrangement providing for adjustment ofthe resistance introduced in the circuitof relay, i35.' The pivotedarmature I4I of this relay is coupled with the source of current B by awire I42, and the contact I43 with which armature MI is adaptedtocooperate is coupled by a wire I44 with one terminal of solenoidfl I6.The other terminal of this solenoid is connected with thesource ofcurrent B as indicated at I45. a u f The circuits just described providefor introduction 'of' a predetermined time delay in actuatlon ofsolenoid I16 the extent of the delay being adjustable by varying theamount of resistance (I39) included in the circuit of the relay I35.Thus, the pilot may predeterminedly set the control I38 for, therheostat toprovide any desired time delay between disconnection. ofthetrols in association with otherfeatures illustrated in Figure 1,including rotor brake and wheel brake controls, and. the by-pass aroundthe master valve, which is automatically opened when the 6 aircraftleaves the groundend automatically closed when the aircraft alights.

Iclaim: I f q 1 For an aircraft having ava'riable pitch sus tainingrotorand mechanism for driving the rotor including a disconnectibledevicetmechanism for varying the rotor blade pitch angle between asubstantially zero pitch setting and a positive rotor drive clutch a'ndincrease of rotor'blade pitch, the entire system being tripped merely bya single control organ, i. e., theswitch I34 which, as above indicated,is preferably mounted either in association with the control wheel orwith the engine throttle. Q j

The circuits of Figure 11 further include a cutout for the timedelayrelay. For this purpose a pair of contacts I 46 and I41 arepositioned to cooperate with a switch part I49 mounted on the controlI38 for the rheostat. Contact I46 is connected by a wire I49 withconnection I26 and contact I41 iscoupled by a wireISII with connectionI44.

This cut-out maybe operated by moving the control handle I39 to aposition beyond the range of rheostat I39, to close the circuit betweencontacts I46 and I 41, thereby cutting out the time delay relay, so thatactuation ofthe trip switch I34simultaneously actuates both solenoids(3H6 and H1) in consequence of which take-off may be eflectedsubstantially without delay between rotor clutch disconnection and bladepitch increase. The system of Figure 11, therefore, is capable ofoperation in a variety of different ways in order to meet varyingoperating conditions, at the will of the pilot. u

The use of a control for effecting take-or! such as the trip switches ofFigures 10 and 11) mounted in association with the flight, controlorgan, is of particular, advantage because of the fact that ineffectlng'the take-01f the rapid increase in rotor thrust may tend tocause the machine to nose downwardly or, upwardly to anundesirabledegree in the eventthat the loading or weight distribution at .the timeof any particular take-oft is such as to provide a center of gravitylocation appreciably ahead of or behind the rotor lift line. With thetake-oil control mounted on the flight control organ, no movement of thepilot's hand is required between the take-oil? control and the flightcontrol and the pilot may, therefore, adjust the flight controlimmediately upon and during the take-off to compensate for anynose-up ornose-down tendency. With respect to the modified controls of Figures 9,10 and 11, it is to be understood that in each autorotational pitchsetting, means for actuating said device to connect and disconnect therotor drive, and a control system for said pitch varying mechanism andfor said actuating means includ ingmechanism operated by take-off oitheaircraft and connectedjwith the pitch varying mechanism to render thepitch varying mechanism incapable of changin the blade pitch angle fromsaid autorotational pitch setting to said substam tially zeropitchsetting when the aircraft takes off, and said mechanism operated bytake-01f further being connected with the means for actuating the devicefor connecting and disconnecting the rotor drive to render saidactuating means incapable of connecting the rotor drive mechanism.when'the aircraft takes off. u

2. A construction in accordance withclaim 1, and further incorporatinginterlock means providing against connection of the rotor drive unlessthe blade pitch angle has been reduced to the substantially zero pitchposition. u

3. For an aircraft having a variable pitch sustaining rotorwith a rotorbrake associated therewith and mechanism for driving the rotor includinga disconnectible device, mechanism for varying the rotor blade pitchangle between a substantially zero pitch setting and a positiveautorotational pitch setting, means for actuating said device to,connect anddisconnect the rotor drive, mecha-nisminterrelating theoperation of the rotor brake and said disconnectible device andincluding means providing against application of the rotor brake whenthe rotor drive is connected, and a control system for 'said pitchvarying mechanism and for said actuating means including mechanismoperated by take-oil of the aircraft and connected with the pitchvarying mechanism to render the pitch varying mechanism incapable ofchanging the blade pitch angle to said substantially zero pitch settingwhen the aircraft takes off, and said mechanism operated by take-o1!further being connected with the means for actuating the device forconnecting and disconnecting the rotor drive torender said actuatingmeansincapable of connectingtthe rotor drive mechanism when the aircrafttakes off.

4. For an aircrait having a substaining rotor,

rotor drive mechanism incorporating a disconnectible device, andalanding wheel having a brake associated therewith, a control systemincluding mechanism interrelating the operation of thedlsconnectibledevice and the wheel (brake and providingagainstconnectioniof the rotor connected with the pitch varyingmechanism to render the pitch varying mechanism incapable of changingthe blade pitch angle to said substantially zero pitch setting.

6. A construction in accordance with claim 5, wherein said mechanism forpreventing undesired pitch reduction after take-off comprises a membermovable to different positions under the influence of landing andtake-off of the aircraft.

7. A construction in accordance with claim 5, wherein the mechanism forvarying the rotor blade pitch angle comprises a fluid pressure systemwith valve means for rendering said system effective or ineffective toreduce the blade pitch angle, and wherein said mechanism for preventingundesired pitch reduction after take-off comprises an additional valveassociated with said fluid pressure system, and .means operated bytake-off of the aircraft to adjust said additional valve to render saidfluid pressure system incapable of effecting undesired blade pitchreduction.

8. For an aircraft having a variable pitch sustaining rotor, a fluidpressure control system for varying the blade pitch including a valveadjustable between positions in which the pressure fluid is effectiveand ineifective to reduce the blade pitch, an additional valveassociated with said system for rendering the first valve effective orineffective, and means operated by landing and take-off of the aircraftto adjust the additional valve to respectively provide conditions inwhich the first valve is effective and ineffective to reduce the rotorblade pitch angle.

9. A construction in accordance with claim 8, wherein the first valve isadjustable during flight of the craft into its position providing forblade pitch reduction, whereby upon landing of the aircraft theconsequent actuation of the second valve automatically effects bladepitch reduction.

10. For an aircraft having a variable pitch sustaining rotor and a rotordrive mechanism incorporating a disconnectible device, a control systemfor varying the blade pitch and for actuating said disconnectible deviceto connect and disconnect the rotor drive, said system including amanually operable control adjustable between positions providing forblade pitch increase and blade pitch decrease and to connect anddisconnect the rotor drive, a second manually operable controlassociated with the control system for rendering the first controleffective or ineffective, and means operated by landing and take-off ofthe aircraft to adjust the second control to respectively provideconditions in which the first control is effective and ineffective toreduce the rotor blade pitch angle and connect the rotor drive. i

11. A construction in accordance with claim 10, in which actuation ofsaid first control in one sense sequentially effects reduction of bladepitch and then connection of the rotor drive,

- the said first control being adjustable during flight into itsposition providing for blade pitch reduction, whereby upon landing ofthe aircraft the consequent actuation of the second controlautomatically effects blade pitch reduction.

12. For an aircraft having a variable pitch sustaining rotor, a rotordrive mechanism incorporating a disconnectible device, and a landingwheel with a brake associated therewith, a control system for varyingthe blade pitch and for actuating said disconnectible device to connectand disconnect the rotor drive, said system including a manuallyoperable control adjustable between positions providing for pitchincrease and pitch decrease and to connect and disconnect the rotordrive, a second control associated with said system for rendering thefirst control effective or ineffective, means operated by landing and.take-off of the aircraft toadjust the second control to respectivelyprovide conditions in which the first control is efiective andineffectlve to reduce the rotor blade pitch angle and connect the rotordrive, and means interlocking the operation of said first control and ofthe wheel brake and providing against actuation of the first control toconnect'the rotor drive unless the wheel brake is applied.

13. A construction in accordance with claim 12, in which actuation ofthe first control in one sense sequentially effects reduction of bladepitch and then connection of the rotor drive, the said first controlbeing adjustable during flight of the craft into its position providingfor blade pitch reduction, whereby upon landing of the aircraft theconsequent actuation of the second control automatically effects bladepitch reduction.

14. A construction in accordance with claim 12, and further including amanually operable further incorporating a manually operable control forth wheel brake, and means operated by actuation of the second controlwhen the aircraft leaves the ground to-render the brake controlinefiective.

16. For an aircraft having a variable pitch sustaining rotor and a rotordrive mechanism incorporating a disconnectible device, a fluid pressurecontrol system for varying'thev blade pitch and for actuating saiddisconnectible device to connect and disconnect the rotor drive, saidsystem including a valve adjustable between positions in which thepressure fluid-is effective and ineffective to reduce the blade pitchand to connect the rotor drive, an additional valveassociated with saidsystem for rendering the first valve effective or ineffective, and meansoperated by landing and take-off of the aircraftto adjust the secondvalve to respectively provide conditions in which the first valve iseffective and ineifectiveto reduce the rotor blade pitch angle andconnect the rotor drive.

17. A construction in accordance with claim 16, in which actuation ofthe first valve in one sense sequentially effects reduction of bladepitch and then connectionof the rotor drive, the said first valve beingadjustable during flight of the craft into its position providing forblade pitch reduction, whereby upon landing of the aircraft theconsequent'actuation of the second valve automatically effects bladepitch reduction.

18. For an aircraft having avariable pitch sustaining rotor, an enginewith a speed control therefor, and mechanism'for driving the rotorincluding a disconnectible device, and a control system for the rotorblade pitch angle and for the rotor drive disconnecting device includingmeans providing for drive of the rotor at a low blade pitch angle, meansproviding for conjoint disconnection of the drive and increase of theblade pitch angle, and a manual control element for actuating said lastmean to disconnect the rotor drive and increase the blade pitch, saidcontrol element being closely associated with the engine speed controlto provide for operation thereof and of the speed control by one hand ofthe pilot without necessitating movement of said hand from one controlto the other.

19. A construction in accordance with claim 18, wherein the meme speedcontrol takes the form of a displaceable member having a hand grip andin which said controlfor disconnecting the rotor drive and increasingthe blade pitch i associated with said hand grip. 1 i

20. l br an aircraft having a variable pitch sustaining rotor, an enginewith a speed control therefor, and mechanism for driving the rotorincluding a disconnectible device, a control system for the rotor bladepitch angle and for the rotor drive disconnecting device including meansproviding for conjoint operation thereof, saidsystem including amanually operable control for actuating said means closely associatedwith the engine speed control to provide for operation thereof and ofthe speed control by one hand of the pilot without necessitatingmovement of said hand from one control to the other.

21. For an aircraft having a variabl pitch sustaining rotor, an enginewith a speed control therefor, and mechanism for driving the rotorincluding a disconnectible device, a control system for the rotor bladepitch angleand for the rotor drive disconnecting device including amanually operable control, and mechanism providing for actuation of thecontrol system to increase the blade pitch including means biasing saidmanually operable control to it position in which the blade pitch angleis increased, a latch for retaining said manually operable control inthe position last mentioned, and means for tripping said latch closelyassociated with the engine speed control to provide for operation,thereof and of the speed control by one hand of the pilot withoutnecessitating movement of said hand from one control to the other.

22. A construction in accordance with claim 21, in which the means fortripping said latch comprises an electro magnetic device. a

23. For an aircraft having a variable pitch sustaining'rotor with abrake associated therewith,

a hydraulic control system for the rotor blade pitch and for the rotorbrake including a hydraulic device for actuating .the rotor brake, ahydraulic device for changing the blade pitch, a. piston-and cylinderdevicefor delivering pressure fluid to-the brak eapplying device, asource of fluid pressure, valve means for delivering pressure fluid fromsaid source to the pitch varying device. and a servo actuating means torsaid piston and cylinder device utilizing the pressure fluid of saidsource to eflect application of the rotor brake. w

24. A construction in accordance with claim 23, and furtherincorporating manually operable means for actuating said piston andcylinder device to apply the rotor brake, whereby said brake 25. For anaircraft having a variable pitch sustaining rotor and a landing wheelwith a brake associated therewith, a hydraulic control system -for therotor blade pitch and for the wheel brake including a hydraulic devicefor actuating the wheel brake, a hydraulic device for changing the bladepitch, means for delivering pressure fluid to the brake applying device,a source of fluidpressure, a valve for delivering pressure fluid fromsaid source to the pitch varying device, and a servo actuating mechanismfor said means utilizing the pressure fluid of said source to effectapplication of the wheel brake.

26. A construction in accordance with claim 25, and furtherincorporating a manually actuated member for actuating said means toapply the wheel brake, whereby said brake may be operatednotwithstanding failure of said source of fluid under pressure.

27. For an aircraft having a variable pitch sustaining rotor and adisoonnectible rotor drive,

a control system providing for sequential disconnection of the rotordrive and increase of blade pitch in that order, a time delay deviceproviding an interval between disconnection of the rotor drive andincrease of blade pitch, and adjustable means for predetermining theperiod of time delay of said device.

28. For an aircraft having a variable pitch sustaining rotor and adisconnectible rotor drive, a control system providing for sequentialdisconnection of the rotor drive and increase of blade pitch in thatorder, a time delay device providing an interval between disconnectionof the rotor drive and increase of blade pitch, and means for renderingsaid time delay device ineflective.

29. A construction in accordance with claim 28, and furtherincorporating adjustable means for predetermining the period of timedelay of said device.

30. For an aircraft having a variable pitch sustaining rotor and adisconnectible rotor drive,

a control system including interlocking control source of fluid underpressure.

connections positivelyassuring sequential disconnection of the rotordrive and increase of blade pitch in that order, said system furtherincluding manually operable control means for actuating the controlsystem to disconnect the rotor drive,

and manually operable control means for actuating the control system toincrease the blade pitch, said two manually operable control means beingsequentially operable in any timed relation determined by the pilot.

31 For an aircraft having a variable pitch sustaining rotor, adisconnectible rotor drive and a flight control organ, a control systemincluding 1 means pro-establishing an operating inter-relation betweenmean rotor blade pitch variation and connection and disconnection of therotor drive. and a manually operable control member for actuating saidcontrol system mounted in association with the flight control organ foractuation by one hand of the pilot without moving said hand from onecontrol to the other.

AGNEW E. LARSEN.

